This invention relates to a unique roller for a cam brake wherein the edges are rounded to relieve potential strains and stresses.
Cam brakes are widely used in heavy vehicle braking systems. Essentially, a rotating cam is controlled by a brake actuator. Rotation of the cam causes two rollers to move radially inwardly or outwardly. The rollers in turn, move brake shoes to pivot and bring friction surfaces into contact with a wheel drum. The friction surfaces thus retard rotation of the drum.
Certain deficiencies exist with the known cam brake systems. In particular, the rollers act as an interface between the brake shoes and the cam. Spring forces on the shoes apply a force to the rollers. Rotation of the cam applies an actuating force to the rollers in a direction opposed to that from the shoes. Large forces are thus transferred through the rollers. Typically, the rollers include relatively small shafts mounting brake shoe webs at two axially spaced locations. A relatively greater diameter portion of the roller contacts the cam.
Due to manufacturing tolerances and assembly inaccuracies, it will often occur that the force from the two webs of the brake shoe are unequally distributed to the rollers. When this occurs, the roller may sometimes become skew or misaligned such that only an edge of the roller contacts the cam. That is, there is effective line contact between the roller and the cam at one edge of the roller. This is undesirable, and can lead to fracturing of the roller, thus limiting its life. While some rollers may have chamfered edges or even rounded surfaces, these have not been over a sufficient distance or at proper locations to act as a cam contacting surface.